![\"Piston](\"http:\/\/lostbiro.com\/blog\/wp-content\/uploads\/2007\/02\/pistontool.jpg\")
<\/p>\nWell, after about six years faithful service, my daughter’s postie bike (Honda CT110) began getting hard to start, and when it did, it started blowing smoke. I checked the compression and realised that the engine was down to about one-third the compression it should have. The dial read about 32 psi, when it should have been over 100. With a couple of weeks to go before my daughter was due to head overseas we just poured in some treacle-like ‘smoke free’ which brought the compression up to about 42 psi – still very low.<\/p>\n
With the bike in storage I decided it was time to find out what the problem really was. My suspicion was a broken oil ring on the piston. I spent one evening last week removing the footpegs, bash-plate sub-frame and the exhaust pipe.<\/p>\n
And today I set to work in earnest. It took less time than I expected. I began by removing the carby (two 10mm bolts) then followed the Clymer manual beginning with ensuring the piston was at top dead centre on the compression stroke.<\/p>\n
I had also previously made a ‘piston holding fixture’ which you can buy as a special tool or make one from wood. The instructions were in the manual – for info you need a piece of wood 1\/2inch x 1-1\/4inch x 4 inches. and you just drill a 1\/2inch hole in the centre and then cut away from one end until you have a fork – like this<\/p>\n
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And it worked perfectly.<\/p>\n
But I digress… After removing the camshaft and with care to ensure that the cam chain did not slide down into the crankcase the head was removed. I used wire threaded through the cam chain to ensure it remained above the cylinder.<\/p>\n
There was some carbon on the piston crown, and some deposits on the valves. The piston holding tool worked very well, but I needed to explore further. On removing the cylinder I found that the piston rings were quite worn, and that the oil ring was in three parts – clearly that is where the problem lies.<\/p>\n
So it was time to remove the piston. This is secured to the connecting rod by two spring clips – not easy to see, but observing a small cutaway on the side of the piston, I noted a hint of a clip. With a pair of needle-nosed pliers it was a brief job to remove the clip from each side. I used a short piece of 1\/2inch dowel to push out the piston pin and the piston was free.<\/p>\n
After cleaning the worst of the carbon with a wire brush and fine emory paper I saw another issue – the top compression ring had at some point worn so thin that it had gouged the groove in which it sat, allowing for movement.<\/p>\n
![\"CT110](\"http:\/\/lostbiro.com\/blog\/wp-content\/uploads\/2007\/02\/ct110pistonbroke.jpg\")
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So it is likely we will need a new piston. But the bore seems unscratched and with luck I will be able to find a new piston to match. And that is a story for later in the week.<\/p>\n
Meanwhile, there is a rather sad looking Honda CT110, with rags to prevent the entry of dust, sitting in my garage awaiting some new parts.<\/p>\n
![\"Honda](\"http:\/\/lostbiro.com\/blog\/wp-content\/uploads\/2007\/02\/ct110repairs.jpg\")
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And the rest awaits reassembly on a nearby table<\/p>\n
![\"CT110](\"http:\/\/lostbiro.com\/blog\/wp-content\/uploads\/2007\/02\/ct110parts.jpg\")
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In the meantime, you can read more about this wonderful bike<\/strong><\/a> People actually race these things, and every year there is a Postie Bike Challenge in Australia where people ride these things from Brisbane to Adelaide (2005), or Ayre’s Rock (Ulluru)(2006). And this year 16-27 October the Postie Bike Challenge<\/strong><\/a> is from Brisbane to Cairns (over 3000kms) on some of the roughest and most beautiful country in Australia<\/p>\n